Creation of ^7LI and Destruction of ^3HE, ^9BE, ^10B, and ^11B in Low-Mass Red Giants, Due to Deep Circulation

Details Creation of ^7LI and Destruction of ^3HE, ^9BE, ^10B, and ^11B in Low-Mass Red Giants, Due to Deep Circulation Creation of ^7LI and Destruction of ^3HE, ^9BE, ^10B, and ^11B in Low-Mass Red Giants, Due to Deep Circulation

Jan 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999apj...510..217s&link_type=abstract

The Astrophysical Journal, Volume 510, Issue 1, pp. 217-231.

Astronomy and Astrophysics

Astronomy

103

Galaxy: Abundances, Nuclear Reactions, Nucleosynthesis, Abundances, Stars: Abundances, Stars: Agb And Post-Agb

Scientific paper

It has been demonstrated that ^7Li can be created in low-mass red giant stars via the Cameron-Fowler mechanism, due to extra deep mixing and the associated ``cool bottom processing.'' Under certain conditions, this ^7Li creation can take the place of the ^7Li destruction normally expected. Note that such extra mixing on the red giant branch (RGB) has previously been invoked to explain the observed ^13C enhancement. This new ^7Li production can account for the recent discovery of surprisingly high lithium abundances in some low-mass red giants (a few of which are superrich lithium stars, with abundances higher than that in the interstellar medium). The amount of ^7Li produced can exceed logepsilon(^7Li)~4, but depends critically on the details of the extra mixing mechanism (mixing speeds, geometry, episodicity). If the deep circulation is a relatively long-lived, continuous process, lithium-rich RGB stars should be completely devoid of beryllium and boron. Cool bottom processing leads to ^3He destruction in low-mass stars; in contrast to the ^7Li creation, the extent of ^3He depletion is largely independent of the details of the extra mixing mechanism. The overall contribution from solar-metallicity stars (from 1 to 40 M_solar) is expected to be a net destruction of ^3He, with an overall ^3He survival fraction g_3~0.9+/-0.2 (weighted average over all stellar masses); this is in contrast to the conclusion from standard dredge-up theory, which would predict that stars are net producers of ^3He (with g^dr_3~2.4+/-0.5). Population II stars experience even more severe ^3He depletion, with 0.3<~g_3<~0.7. Destruction of ^3He in low-mass stars is consistent with the requirements of Galactic chemical evolution models; it would also result in some relaxation of the upper bound on the primordial (D+^3He)/H abundance, thus relaxing the lower bound on the cosmic baryon density Omega_b from big bang nucleosynthesis calculations. For reference, we also present the effects of standard first and second dredge-up on the helium, lithium, beryllium, and boron isotopes.

Affiliated with

Also associated with

No associations

Rating

Creation of ^7LI and Destruction of ^3HE, ^9BE, ^10B, and ^11B in Low-Mass Red Giants, Due to Deep Circulation does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Creation of ^7LI and Destruction of ^3HE, ^9BE, ^10B, and ^11B in Low-Mass Red Giants, Due to Deep Circulation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Creation of ^7LI and Destruction of ^3HE, ^9BE, ^10B, and ^11B in Low-Mass Red Giants, Due to Deep Circulation will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1189868